For fuel cell power generators employed in military field deployment, the use of logistic fuels (such as diesel, JP-5, JP-8, and the like) as the primary energy source is highly desired due to the high energy densities, economics and wide availability of these fuels. However, these fuels typically contain high concentrations of sulfur compounds (up to 3000 ppm according to the MIL-DTL-83133G) and, if not removed, they can cause severe poisoning and deactivation to solid oxide fuel cell (SOFC) anodes, as well as fuel reformers. Sulfur exists in these fuels as various compounds. These include sulfides, dimethylbenzothiophene, trimethylbenzothiophene, mercanptans, thiols, thiophenes, alkyl-substituted benzothiophenes (BT) and dibenzothiophenes (DBT) with the increased boiling point and difficulty to remove in that order. Dimethylbenzothiophene and trimethylbenzothiophene are the two major sulfur compounds in military jet fuels. Alkyl-substituted BT and DBT are typically called “refractory” sulfur species because they are more difficult to desulfurize compared to un-substituted counter parts. To avoid sulfur-poisoning, reduction of sulfur in reformate to sub-ppm levels is generally required for SOFC-based generators.
Various desulfurization systems have been developed for integration with liquid fuel based fuel cell systems. These systems generally employ one of the two approaches for sulfur removal: direct organic sulfur absorption (DOSA) or reaction-assisted H2S adsorption, depending on whether reactions are used to first convert the refractory organic sulfur to more easily absorbed inorganic H2S. Regardless of which approach is employed, a sorbent material is typically used to immobilize the sulfur from the fuel or reformate stream.
However, due to the complexity and the weight of these desulfurization systems, it would be desirable to provide portable desulfurization systems and methods that would be available in a theater of operation and permit fuel cartridges to be filled and refilled from this supply.